Caloric materials near ferroic phase transitions

Warburg is widely credited with the first experimental observation of MC effects

X. Moya; S. Kar-Narayan; N. D. Mathur

2014

Scholarcy highlights

  • Warburg is widely credited with the first experimental observation of MC effects
  • Just after the 1930 experimental observation of electrically analogous EC effects in Rochelle salt, MC cooling in paramagnetic salts was exploited to approach absolute zero
  • The giant mC effects were found in the shape-memory alloy Cu69.6Al27.7Ni2.7 as part of a thermodynamic study into martensitic transitions; the giant MC effects were found near the magnetostructural transition in metallic Fe49Rh51; and the giant EC effects were found near the ferroelectric transition in films of the ceramic PbZr0.95Ti0.05O3 and later two fluorinated polymers
  • There are likely to be many multicaloric materials given that the structural degree of freedom, which underpins mC effects, is typically responsible for enhancing MC and EC effects
  • Near finite-temperature magnetic phase transitions, laboratory fields corresponding to several tesla can drive substantial MC effects, as seen in the latter half of the twentieth century using crystalline and amorphous materials based on rare-earth and transition-metal elements
  • Existing refrigerators are based on liquid-vapour transitions, and may operate at up to 60% of the Carnot efficiency, as confirmed by two independent industry experts with whom we spoke
  • Driven irreversible heating near room temperature has been exploited for induction cooking and other applications, but it remains to be seen whether reversible caloric effects associated with phase transitions will be exploited in technologically useful devices
  • There is in any case plenty of scope for interesting science, e.g. the development of microscopic theories for the different types of EC materials, investigations of inhomogeneity using modern imaging methods, and studies of caloric effects in materials that might display ferrotoroidic order of a magnetic or electrical nature

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